This invention relates to a spreader for multistage container stacking.
FIGS. 10 to 12 show the outline of a spreader for multistage container stacking for use in a container yard or the like (Japanese Laid-Open Patent Publication No. 77453/97).
FIG. 10 is a perspective view of the left half of a conventional spreader for multistage container stacking. FIG. 11 is a front view as seen along line XI--XI of FIG. 10. FIG. 12 is a sectional view taken along line XII--XII of FIG. 11. FIG. 13 is a layout drawing of a conventional sensor for detection of a container lower end height.
In FIG. 10, the left half of a spreader 1 is shown as a perspective view, with the obliquely upper left direction representing a direction forward of a crane, the obliquely lower right direction representing a direction rearward of the crane, the obliquely lower left direction representing a direction leftward of the crane, and the obliquely upper right direction representing a direction rightward of the crane.
As illustrated in FIG. 10, the spreader 1 is composed of a spreader body 2 suspended at four points by hoisting ropes 4 paid out from the crane (not shown), and a spreader extensible portion 3 to be symmetrically expanded and contracted in the longitudinal direction by a driving mechanism within the spreader body 2 via a power source and a control cable connected from above the crane.
At the end of each protrusion of the spreader extensible portion 3, an end beam 5 is formed. In each of columns at both ends of the end beam 5, a well known twist lockpin 6 is provided as shown in FIG. 11. The twist lock pins 6 are coupled to or detached from upper corner fittings 50a of a container 50 from above to suspend or release the container 50.
From the end beam 5, as will be described later on, a flipper beam 7 is suspended by wires 14. To both ends of the flipper beam 7, a pair of symmetrical corner flippers 8 are integrally fixed. On the vertical side surface part of the corner flipper 8, a flipper lock pin mounting/removing device 9 is provided.
At the middle of the upper surface of the end beam 5, a pair of drums 10 are disposed adjacent and parallel to each other. Synchronous gears 11 are attached to the drums 10 for engaging each other. To one of the drums 10, a driving motor 12 is connected.
On each of support bases 15 of the columns at the opposite ends of the end beam 5, a pair of guide sheaves 13 are provided.
The pair of drums 10 are wound with the end parts of the pair of wires 14. These wires 14 are passed over the respective guide sheaves 13 at the opposite ends of the end beam 5, and guided downward. The other end part of the wire 14 is tied to two locations straddling the center of gravity of the cross sections of the flipper beam 7 and the corner flipper 8 to support the flipper beam 7.
The side surfaces of the columns at the opposite ends of the end beam 5 are each provided with a couple of upper and lower binding openings 5a, 5b which bind to the flipper lock pin mounting/removing device 9.
The upper opening 5a is a flipper pin binding portion foruse in retracting the flipper 8, while the lower opening 5b is a flipper pin binding portion used when the flipper 8 is at a predetermined corner guide position.
Between the side part of the end beam 5 and the side part of the flipper beam 7, a extensible rod type swing suppressor 17 is connected as shown in FIG. 11.
The swing suppressor 17 is composed of a short cylindrical guide 18 supported on an inward part of a low-level mounting base 15a at each of the opposite ends of the end beam 5 by a horizontal shaft 18a so as to be tiltable in the direction of the spreader length; a second cylindrical guide 19 supported in the cylindrical guide 18 by a stop flange 19a at the upper end so as to be slidable within the cylindrical guide 18; an extensible rod 20 supported in the second cylindrical guide 19 by a stop flange 20a at the upper end so as to be slidable within the second cylindrical guide 19; and a swing adjusting cylinder 21 provided on the mounting base 15a so as to be tiltable and having a driving end thereof connected to an upper part of the cylindrical guide 18 so as to be tiltable.
The extensible rod 20, in an expansible and contractible condition, has an eye plate 20b, which is provided at the lower end thereof, connected via a shaft 20c to a bracket 8b overhanging from the corner flipper 8.
Thus, when the cylinder 21 is contractedly driven, the cylindrical guide 18 is turned counterclockwise in FIG. 11. The pair of corner flippers 8 are pressed against the end surface of the container via the second cylindrical guide 19 and the extensible rod 20. At this time, the center of the flipper lock pin mounting/removing device 9 just lies on the vertical center line of the side surface openings of the corner fittings 50a, 50b of the container 50.
Upon the expanding driving of the cylinder 21, the cylindrical guide 18 is turned clockwise in FIG. 11. Thus, the corner flippers 8 are separated from the end surface of the container 50 by a certain distance, and can be hoisted or lowered.
Directly below the flipper lock pin mounting/removing devices 9, photoelectric switches 52 for detecting the lower end of the container are provided in the pair of corner flippers 8 in a direction in which they are opposed to each other, as shown in FIG. 12.
That is, the photoelectric switch 52 is provided downwardly apart from the center of the flipper lock pin mounting/removing device 9 by a distance (L.sub.1 +L.sub.2) which is the sum of the altitudinal distance L.sub.1 from the lower end of the container 50 to the center of the opening of the lower corner fitting 50b, and the lowering distance L.sub.2 from the position of actuation of the photoelectric switch 52 (the lower end of the container) to the position at which the flipper beam 7 stops descending. On the actuation of the photoelectric switch 52, the center of the flipper lock pin mounting/removing device 9 stops at the height of the center of the opening of the lower corner fitting 50b.
In FIG. 12, the numeral 9a denotes a lock pin to be inserted or removed by the flipper lock pin mounting/removing device 9, and the numeral 8a denotes the taper guide surface of the corner flipper 8.
A hydraulic hose and an electric cable (not shown) which are connected from the top of the spreader to the top of the flipper beam 7 are held by an automatically wound reel or the like situated on the spreader. In accordance with the descent of the flipper beam 7, the hydraulic hose and the electric cable are pulled out of the automatically wound reel. As the flipper beam 7 ascends, the hydraulic hose and the electric cable are taken up by the automatically wound reel.
Handling work for the container 50 by the above-described spreader 1 is performed in the following manner:
First, the wires 14 are unwound by the drums 10, and the lock pin 9a is removed and mounted by the flipper lock pin mounting/removing device 9 to move the corner flipper 8 from the position of the upper opening 5a to the position of the lower opening 5b of the spreader 1 and lower the flipper beam 7 onto the container 50 to be hoisted.
Guide by the taper surface 8a of each corner flipper 8 causes the spreader 1 to fit on and land on the container 50. Then, the twist lock pin 6 is fitted into the upper surface hole of the container upper corner fitting 50a to lift the spreader 1 and carry it horizontally.
Then, the carried container 50 is to be stacked on another container in the yard. For this purpose, the flipper lock pin 9a is detached from the lower opening 5b of the spreader 1 during the horizontal carriage. Also, the drums 10 are driven to lower the flipper beam 7, and the flipper pin 9a is inserted into and joined to the side surface opening of the lower corner fitting 50b of the container 50. In this condition, the container 50 is lowered onto another container in the yard.
The carried container 50 is guided by the corner flipper 8 mounted on the lower corner fitting 50b, whereby it is fitted on and landed on another container.
Then, the flipper lock pin 9a is detached from the container lower corner fitting 50b, and the drums 10 are driven to lift the flipper beam 7. The flipper lock pin 9a is inserted into and joined to the lower opening 5b of the spreader 1, and the twist lock pin 6 is released from the carried container 50. Only the spreader 1 is lifted, and moved to the position of the next container 50 to be carried. In this manner, carriage of the container is repeated.
The above-mentioned conventional spreader 1 poses the following problems:
On the bottom surface of the container 50 that often contacts the floor during distribution of the container 50, corrugated board pieces or thin plate pieces may engage into the gap between the frame and the bottom plate, or paper or vinyl pieces may stick to the flat part of the bottom frame via an adherent material or the like.
This foreign matter on the bottom surface of the container 50 poses difficulty in doing the aforementioned work for shifting the flipper beam 7 to the position of the lower corner fitting 50b of the container 50.
Assume, for example, that the photoelectric switch 52 of the spreader 1 for detecting the lower end of the container is a transmission type one comprising a light projector 52a and a light receiver 52b, as shown in FIG. 13(a). The flipper beam 7 descends along the container 50, and goes beyond the lower end of the container 50. If foreign matter 53 adheres to the frame lower surface of the container 50, the foreign matter 53 blocks the light path of the photoelectric switch 52, making the photoelectric switch 52 fail to function. At a position past the foreign matter 53, the photoelectric switch 52 acts with delay. This delay in the actuation of the photoelectric switch 52 is caused even by a tiny foreign matter 53.
Thus, during a handling operation for the container 50, the corner flipper 8 may not be aligned with and fixed to the container lower corner fitting 50b. This may require that the handling work be interrupted, and inspection and correction of abnormalities be performed.
Even when the photoelectric switch 52 detects the lower end of the container at the normal position, a change cannot be avoided in the distance L.sub.2 traveled until the stoppage of the descent of the flipper beam 7. This makes it difficult to align the flipper lock pin 9a with the center of the side surface opening of the container lower corner fitting 50b.
When a single reflection type light projector/receiver 52c is used as the photoelectric switch 52 as in FIG. 13(b), the irregular reflection of light due to the irregularities of the container wall surface makes the precise operation of the photoelectric switch 52c difficult. Foreign matter 53 adhering to the lower surface of the container also precludes the operation of the photoelectric switch 52c.
Furthermore, the hydraulic hose and the electric cable connected from the spreader 1 to the flipper beam 7 wear owing to repeated unwinding and winding. When they are rubbed against the end surface of the container during the upward or downward movement of the flipper beam 7, they may be damaged.